Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$96.84	10.368%	$106.8804	$106.88	$106.90	$106.90
Purchase #2	$17.61	4.748%	$18.4461	$18.45	$18.45	$18.40
Purchase #3	$205.29	9.761%	$225.3284	$225.33	$225.35	$225.30
Purchase #4	$105.91	3.576%	$109.6973	$109.70	$109.70	$109.70
Purchase #5	$158.25	13.377%	$179.4191	$179.42	$179.40	$179.40
Purchase #6	$152.56	12.376%	$171.4408	$171.44	$171.45	$171.40
Purchase #7	$221.75	4.119%	$230.8839	$230.88	$230.90	$230.90
7 purchase totals =	$958.21		$1,042.0960	$1,042.10	$1,042.15	$1,042.00